Modular rotor blade and method for mounting a wind turbine

ABSTRACT

A rotor blade for a wind turbine includes at least two segments, and at least one cable, wherein the at least two segments are adapted to be mounted together to form the rotor blade, and wherein the at least one cable is adapted to attach the at least two segments, and wherein the at least one cable is extending through at least part of the segments. Further, methods for assembling a modular rotor blade and for mounting a wind turbine are provided.

BACKGROUND OF THE INVENTION

The subject matter described herein relates generally to methods and systems for the mounting of wind turbines, and more particularly, to methods and systems for mounting wind turbines having modular rotor blades.

At least some known wind turbines include a tower and a nacelle mounted on the tower. A rotor is rotatably mounted to the nacelle and is coupled to a generator by a shaft. A plurality of blades extend from the rotor. The blades are oriented such that wind passing over the blades turns the rotor and rotates the shaft, thereby driving the generator to generate electricity.

Conventionally, the blades are pre-fabricated in a factory and are transported to the erection site of the wind turbine via land, sea, or air transport. At the site, the rotor is typically mounted on the ground by attaching the rotor blades to the rotor hub, and the assembled rotor is subsequently lifted up to its position at the nacelle by a crane.

During this process, a number of difficulties can occur, which are sometimes based on the characteristics of the terrain at the erection site and around it. As an example, wind turbines in mountain regions or at the coast often have to be transported over small winding roads. Land transport is in these cases hindered by the fact that the rotor blades have a considerable length which limits the ability of a carrying vehicle to follow curves.

Moreover, the space at the erection site may be limited, for instance in mountain regions. Hence, it may hardly, or not at all, be possible to assemble the rotor on the ground, because to this end a plane space in the dimension of more than the diameter of the rotor is necessary.

In view of the above, it is desirable to have wind turbine blades which require less space during transport, and to have a method to assemble and mount a wind turbine rotor in a surrounding with limited space for the assembly process.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a rotor blade for a wind turbine is provided. A rotor blade for a wind turbine includes at least two segments, and at least one cable, wherein the at least two segments are adapted to be mounted together to form the rotor blade, and wherein the at least one cable is adapted to attach the at least two segments, and wherein the at least one cable is extending through at least part of the segments.

In a second aspect, a wind turbine is provided. It includes at least one rotor blade, the rotor blade including at least two segments, and at least one cable, wherein the at least two segments are adapted to be mounted together to form the rotor blade, and wherein the at least one cable is adapted to attach the at least two segments, and wherein the at least one cable is extending through at least part of the segments.

In another aspect, a method for assembling a rotor blade for a wind turbine is provided. The method includes providing at least two segments, providing at least one cable, fixing at least one first end of the at least one cable to at least one segment, tensioning an at least one second end of the cable in order to attach the at least two segments to each other, and fixating the at least one second end of the at least one cable.

Further aspects, advantages and features of the present invention are apparent from the dependent claims, the description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures wherein:

FIG. 1 is a perspective view of an exemplary wind turbine.

FIG. 2 is an enlarged sectional view of a portion of the wind turbine shown in FIG. 1.

FIG. 3 is a perspective view of a modular rotor blade according to embodiments.

FIG. 4 is a perspective view of a modular rotor blade according to further embodiments.

FIG. 5 is a perspective view of a modular rotor blade according to yet further embodiments.

FIG. 6 is a perspective view of a wind turbine rotor during assembly according to embodiments.

FIG. 7 is a perspective view of the wind turbine rotor of FIG. 6 after all rotor blades were mounted.

FIGS. 8 to 10 are perspective views of a wind turbine during mounting according to embodiments.

FIG. 11 is a perspective view of a modular rotor blade according to further embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet further embodiments. It is intended that the present disclosure includes such modifications and variations.

The embodiments described herein include a wind turbine system that can be mounted in regions with limited space for the mounting process. More specifically, the modular rotor blades can be transported to construction sites in locations not easily accessible.

As used herein, the term “blade” is intended to be representative of any device that provides a reactive force when in motion relative to a surrounding fluid. As used herein, the term “wind turbine” is intended to be representative of any device that generates rotational energy from wind energy, and more specifically, converts kinetic energy of wind into mechanical energy. As used herein, the term “wind generator” is intended to be representative of any wind turbine that generates electrical power from rotational energy generated from wind energy, and more specifically, converts mechanical energy converted from kinetic energy of wind to electrical power. As used herein, the term “modular rotor blade” is intended to be representative of a rotor blade which includes at least two segments, and wherein the rotor blade is assembled by mounting the segments.

FIG. 1 is a perspective view of an exemplary wind turbine 10. In the exemplary embodiment, wind turbine 10 is a horizontal-axis wind turbine. Alternatively, wind turbine 10 may be a vertical-axis wind turbine. In the exemplary embodiment, wind turbine 10 includes a tower 12 that extends from a support system 14, a nacelle 16 mounted on tower 12, and a rotor 18 that is coupled to nacelle 16. Rotor 18 includes a rotatable hub 20 and at least one rotor blade 200 coupled to and extending outward from hub 20. In the exemplary embodiment, rotor 18 has three rotor blades 200, which are modular rotor blades. In an alternative embodiment, rotor 18 includes more or less than three rotor blades 200. In the exemplary embodiment, tower 12 is fabricated from tubular steel to define a cavity (not shown in FIG. 1) between support system 14 and nacelle 16. In an alternative embodiment, tower 12 is any suitable type of tower having any suitable height.

Rotor blades 200 are spaced about hub 20 to facilitate rotating rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. Rotor blades 200 are mated to hub 20 by coupling a blade root portion 24 to hub 20 at a plurality of load transfer regions 26. Load transfer regions 26 have a hub load transfer region and a blade load transfer region (both not shown in FIG. 1). Loads induced to rotor blades 200 are transferred to hub 20 via load transfer regions 26.

In one embodiment, rotor blades 200 have a length ranging from about 15 meters (m) to about 91 m. Alternatively, rotor blades 200 may have any suitable length that enables wind turbine 10 to function as described herein. For example, other non-limiting examples of blade lengths include 10 m or less, 20 m, 37 m, or a length that is greater than 91 m. As wind strikes rotor blades 200 from a direction 28, rotor 18 is rotated about an axis of rotation 30. As rotor blades 200 are rotated and subjected to centrifugal forces, rotor blades 200 are also subjected to various forces and moments. As such, rotor blades 200 may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.

Moreover, a pitch angle or blade pitch of rotor blades 200, i.e., an angle that determines a perspective of rotor blades 200 with respect to direction 28 of the wind, may be changed by a pitch adjustment system 32 to control the load and power generated by wind turbine 10 by adjusting an angular position of at least one rotor blade 200 relative to wind vectors. Pitch axes 34 for rotor blades 200 are shown. During operation of wind turbine 10, pitch adjustment system 32 may change a blade pitch of rotor blades 200 such that rotor blades 200 are moved to a feathered position, such that the perspective of at least one rotor blade 200 relative to wind vectors provides a minimal surface area of rotor blade 200 to be oriented towards the wind vectors, which facilitates reducing a rotational speed of rotor 18 and/or facilitates a stall of rotor 18.

In the exemplary embodiment, a blade pitch of each rotor blade 200 is controlled individually by a control system 36. Alternatively, the blade pitch for all rotor blades 200 may be controlled simultaneously by control system 36. Further, in the exemplary embodiment, as direction 28 changes, a yaw direction of nacelle 16 may be controlled about a yaw axis 38 to position rotor blades 200 with respect to direction 28.

In the exemplary embodiment, control system 36 is shown as being centralized within nacelle 16, however, control system 36 may be a distributed system throughout wind turbine 10, on support system 14, within a wind farm, and/or at a remote control center. Control system 36 includes a processor 40 configured to perform the methods and/or steps described herein. Further, many of the other components described herein include a processor. As used herein, the term “processor” is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. It should be understood that a processor and/or a control system can also include memory, input channels, and/or output channels.

In the embodiments described herein, memory may include, without limitation, a computer-readable medium, such as a random access memory (RAM), and a computer-readable non-volatile medium, such as flash memory. Alternatively, a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, input channels include, without limitation, sensors and/or computer peripherals associated with an operator interface, such as a mouse and a keyboard. Further, in the exemplary embodiment, output channels may include, without limitation, a control device, an operator interface monitor and/or a display.

Processors described herein process information transmitted from a plurality of electrical and electronic devices that may include, without limitation, sensors, actuators, compressors, control systems, and/or monitoring devices. Such processors may be physically located in, for example, a control system, a sensor, a monitoring device, a desktop computer, a laptop computer, a programmable logic controller (PLC) cabinet, and/or a distributed control system (DCS) cabinet. RAM and storage devices store and transfer information and instructions to be executed by the processor(s). RAM and storage devices can also be used to store and provide temporary variables, static (i.e., non-changing) information and instructions, or other intermediate information to the processors during execution of instructions by the processor(s). Instructions that are executed may include, without limitation, wind turbine control system control commands. The execution of sequences of instructions is not limited to any specific combination of hardware circuitry and software instructions.

FIG. 2 is an enlarged sectional view of a portion of wind turbine 10. In the exemplary embodiment, wind turbine 10 includes nacelle 16 and hub 20 that is rotatably coupled to nacelle 16. More specifically, hub 20 is rotatably coupled to an electric generator 42 positioned within nacelle 16 by rotor shaft 44 (sometimes referred to as either a main shaft or a low speed shaft), a gearbox 46, a high speed shaft 48, and a coupling 50. In the exemplary embodiment, rotor shaft 44 is disposed coaxial to longitudinal axis 116. Rotation of rotor shaft 44 rotatably drives gearbox 46 that subsequently drives high speed shaft 48. High speed shaft 48 rotatably drives generator 42 with coupling 50 and rotation of high speed shaft 48 facilitates production of electrical power by generator 42. Gearbox 46 and generator 42 are supported by a support 52 and a support 54. In the exemplary embodiment, gearbox 46 utilizes a dual path geometry to drive high speed shaft 48. Alternatively, rotor shaft 44 is coupled directly to generator 42 with coupling 50.

Nacelle 16 also includes a yaw drive mechanism 56 that may be used to rotate nacelle 16 and hub 20 on yaw axis 38 (shown in FIG. 1) to control the perspective of rotor blades 200 with respect to direction 28 of the wind. Nacelle 16 also includes at least one meteorological mast 58 that includes a wind vane and anemometer (neither shown in FIG. 2). Mast 58 provides information to control system 36 that may include wind direction and/or wind speed. In the exemplary embodiment, nacelle 16 also includes a main forward support bearing 60 and a main aft support bearing 62.

Forward support bearing 60 and aft support bearing 62 facilitate radial support and alignment of rotor shaft 44. Forward support bearing 60 is coupled to rotor shaft 44 near hub 20. Aft support bearing 62 is positioned on rotor shaft 44 near gearbox 46 and/or generator 42. Alternatively, nacelle 16 includes any number of support bearings that enable wind turbine 10 to function as disclosed herein. Rotor shaft 44, generator 42, gearbox 46, high speed shaft 48, coupling 50, and any associated fastening, support, and/or securing device including, but not limited to, support 52 and/or support 54, and forward support bearing 60 and aft support bearing 62, are sometimes referred to as a drive train 64.

In the exemplary embodiment, hub 20 includes a pitch assembly 66. Pitch assembly 66 includes one or more pitch drive systems 68 and at least one sensor 70. Each pitch drive system 68 is coupled to a respective rotor blade 200 (shown in FIG. 1) for modulating the blade pitch of associated rotor blade 200 along pitch axis 34. Only one of three pitch drive systems 68 is shown in FIG. 2.

In the exemplary embodiment, pitch assembly 66 includes at least one pitch bearing 72 coupled to hub 20 and to respective rotor blade 200 (shown in FIG. 1) for rotating respective rotor blade 200 about pitch axis 34. Pitch drive system 68 includes a pitch drive motor 74, pitch drive gearbox 76, and pitch drive pinion 78. Pitch drive motor 74 is coupled to pitch drive gearbox 76 such that pitch drive motor 74 imparts mechanical force to pitch drive gearbox 76. Pitch drive gearbox 76 is coupled to pitch drive pinion 78 such that pitch drive pinion 78 is rotated by pitch drive gearbox 76. Pitch bearing 72 is coupled to pitch drive pinion 78 such that the rotation of pitch drive pinion 78 causes rotation of pitch bearing 72. More specifically, in the exemplary embodiment, pitch drive pinion 78 is coupled to pitch bearing 72 such that rotation of pitch drive gearbox 76 rotates pitch bearing 72 and rotor blade 200 about pitch axis 34 to change the blade pitch of blade 200.

Pitch drive system 68 is coupled to control system 36 for adjusting the blade pitch of rotor blade 200 upon receipt of one or more signals from control system 36. In the exemplary embodiment, pitch drive motor 74 is any suitable motor driven by electrical power and/or a hydraulic system that enables pitch assembly 66 to function as described herein. Alternatively, pitch assembly 66 may include any suitable structure, configuration, arrangement, and/or components such as, but not limited to, hydraulic cylinders, springs, and/or servo-mechanisms. Moreover, pitch assembly 66 may be driven by any suitable means such as, but not limited to, hydraulic fluid, and/or mechanical power, such as, but not limited to, induced spring forces and/or electromagnetic forces. In certain embodiments, pitch drive motor 74 is driven by energy extracted from a rotational inertia of hub 20 and/or a stored energy source (not shown) that supplies energy to components of wind turbine 10.

FIG. 3 shows an exemplary embodiment of a modular rotor blade 200 during the assembly process. In the exemplary embodiment, the rotor blade 200 includes three segments 210, 220, 230 and a cable 260. Each segment 210, 220, 230 includes at least one contact face 240.

FIG. 4 shows the rotor blade of FIG. 3, wherein elements not visible in FIG. 3 are depicted with dashed lines. Cable 260 is fixed inside the tip element 230 of the rotor blade to a fixation element 290. In the embodiment, this fixation is realized by laminating the end of the cable to the fixation element 290. In other embodiments, other fixation methods are applied, such as clamping. From the fixation element, cable 260 protrudes through tube 280 in a direction to middle element 220. It further protrudes through another tube 280 into middle element 220 and protrudes out of middle element 220 through a further tube 280. The cable enters root element 210 via another tube 280 and leaves the element via opening 265. Hence, cable 260 protrudes from its fixing point in the tip element 230 through the rotor blade elements. In the embodiment, the end of cable 260 opposite to the end fixed to the tip element 230 leaves root element 210 via opening 265. Tubes 280 may have different lengths. In embodiments, they each have a length from 2 cm up to the entire length of the respective rotor blade segment. More specifically, the length is from 5 cm to 1 m, even more specifically from 10 cm to 40 cm. That is, in some embodiments, one tube 280 may extend from one end of the segment to the other, whereas in other embodiments, one tube 280 is provided at each end portion of the rotor blade segment 210, 220. Tip segment 230 typically has only one tube provided at one end.

In the exemplary embodiment, modular rotor blade 200 is mounted by positioning rotor blade elements 210, 220, 230 as shown in FIG. 3 and FIG. 4. Cable 260 may be fixed to tip element 230 at or from the factory, and may only be inserted through the other elements 220, 210 at the construction site of the wind turbine. In other embodiments, cable 260 may also be applied and fixed to tip element 230 during the assembly process at the site. In this case, tip element 230 has to be designed such that the cable may be mounted or fixed to fixation element 290 at the erection site of the wind turbine. Subsequently, a force is applied to the end of the cable 260 protruding out of root element 210. As the other end of the cable is fixed to tip element 230, elements 210, 220, 230 will be tied together, narrowing gaps 215, 225 until the gaps are closed, which includes that contact faces 240 of the segments 210, 220, 230 abut contact faces 240 of adjacent segments 210, 220, 230.

FIG. 5 shows the modular rotor blade 200 of FIGS. 3 and 4 after the gaps 215, 225 have been closed by the tensioning process. After the gaps are closed, tensioning of the cable 260 continues. As the blade elements 210, 220, 230 are in contact at their contact faces 240, no further movement of the blade elements is possible. The tensioning then will lead to an increase of the tension of cable 260. If a predefined tension is reached, the tensioning process is halted and cable 260 is fixated. In the exemplary embodiment, this is achieved by clamping cable 260 via a clamping mechanism 300. Also other fixation methods are possible. The predefined tension of the cable 260 depends strongly on the properties of the modular rotor blade, for instance on its shape, material and construction. The tension in the cable may be measured during the tensioning process by a variety of methods known to a skilled person, for instance, strain elements. In another embodiment, the torque of the winch used for tensioning or pulling cable 260 may be used to define the point at which the tensioning process is complete.

As the cable 260 is fixated while it is under tension, it serves as a fixation element for attaching rotor blade element 210, 220, 230 together. The tension of the cable is calculated such that it is high enough to maintain stability of the assembled modular rotor blade 200 under every possible condition during subsequent mounting and operation of the wind turbine. This includes extreme load cases such as emergency stops during strong winds and the like. Cable 260 typically includes steel, stainless steel, such as V2A or V4A, fiberglass, carbon fiber, or combinations thereof. Depending on the size of the wind turbine installation, the cable 260 may have a diameter from 10 mm to 80 mm, more typically from 20 mm to 70 mm. Tubes 280 typically have a diameter which is about 1 mm to 50 mm, more typically from 3 mm to 30 mm greater than the diameter of the cable. The tubes may comprise metal, fiberglass or any other suitable material. As the tubes typically do not carry significant loads, they do not have to be designed to have a particularly high strength and stiffness, but should be able to withstand the frictional force exerted by the cable 260 moving through it during the mounting process. In other embodiments, tubes 280 are replaced by an assembly of rollers guiding the cable 260, for instance, as a non-limiting example, three cylindrical rollers which are positioned with an offset of 120° to each other. In other embodiments, other roller or tube configurations are employed.

FIGS. 3, 4, and 5 show the modular rotor blade 200 and the principle of the mounting process, respectively the tensioning or pulling process where the applied forces are indicated by arrows. The rotor blades assembled by the above described method may then subsequently be mounted to a rotor hub 320 on the ground. In other embodiments, the assembled rotor blades are individually lifted to their position at the wind turbine tower and mounted to a hub 320, which has been previously mounted to the nacelle 16.

In other embodiments, the number of segments of the blade 200 may be different, for instance, from two elements up to 10 elements.

In the described embodiments, the tensioning force is applied by a winch or a hydraulic cylinder. The tensioning device has to be arranged with respect to the elements of the rotor blades such that the force exerted by the device on the cable will not lead to a movement of the root blade portion 210 relative to the pulling device. In an embodiment, the pulling device, i.e., a winch or hydraulic cylinder, is restrained against front face 295 of root blade element 210. At least rotor blade elements 220 and 230 are supported such that they move freely in the direction which is necessary to follow the force exerted by cable 260. To this end, the elements may be supported on rollers (not shown), in other embodiments they may also be held by a crane. Root blade portion 230 may be stably positioned on the ground, as it typically does not move during the tensioning process.

FIG. 6 shows a further exemplary embodiment, in which the rotor blades 200 are also mounted to the rotor hub 320 during the assembly process of the blades. The figure shows a rotor 350 in the status of being assembled. One rotor blade 360 is already mounted, while another blade is about to be assembled using the tensioning method as described before. Rotor hub 320 is positioned on the ground, such that the longitudinal axis of the flanges or openings for the rotor blades are parallel to the ground. The rotor blade elements 210, 220, 230 are then positioned adjacent to the hub 320 in the manner described with respect to FIGS. 3, 4, and 5. The cable 260 protrudes from root blade element 210 into hub 320. A tensioning device 330, for instance an electrical winch, hydraulic winch, or a hydraulic cylinder, serves for tensioning the cable 260. In the exemplary embodiment, the tensioning device 330 is located outside hub 320. In the embodiment, cable 260 is redirected inside hub 320 via at least one pulley 345 and is subsequently guided out of hub 320 via an opening 335. As mentioned before, the device 330 has to be fixed (not shown) against hub 320 such that the pulling force will not lead to a displacement of tensioning device 330 with respect to the hub 320. In other embodiments, tensioning device 330 may be located inside hub 320. It may be removed after the assembly or remain inside the hub for later use.

FIG. 7 shows a completely assembled rotor 350 lying on the ground after the process shown in FIG. 6. Subsequently, the rotor can be lifted, for instance by a crane, to its position on the wind turbine tower 12.

FIG. 8 shows an exemplary embodiment of assembling a wind turbine having modular rotor blades. The modular rotor blades are similar to the ones described with respect to previous embodiments. First, hub 320 is mounted to the nacelle 16, such that a flange 370 for a rotor blade faces the ground. Subsequently, root blade portion 210 is lifted from the ground up to hub 320. To this end, cable 260 is led through tubes 280 (not shown) of the element and is fixed at a lower end of the element 210. Cable 260 is then towed by a winch 330 (only schematically shown) located in the hub 320 or in the nacelle 16. Depending on the location of winch 320, the cable has to be guided inside the hub and/or nacelle by one or more pulleys (not shown). Once the element 210 is at its designated position at the hub, it is fixed to hub 320. Respective methods are well known to a skilled person. The cable is than loosened from element 210 and one end let down to the ground in order to lift the next element. Subsequently, the same procedure is carried out for element 220 (which is shown in FIG. 8) When element 220 is towed up and is in contact with root blade element 210, it is fixed at this position. This may be carried out by attaching the elements 210, 220 together via screws and bolts, or via an additional cable holding element 220 from the hub or nacelle. The cable 260 is then released from element 220.

FIG. 9 shows how the tip element 230 of a first rotor blade to be mounted is towed up to elements 210, 220 already in place. As in the embodiments described with respect to FIGS. 3, 4, and 5, once element 230 is in place, the tensioning process is continued until the tension of the cable 260 has reached a predefined value. Cable 260 is then fixated inside hub 320 via a clamping mechanism. Once a first rotor blade is completed, the hub 320 is turned until another flange 370 faces the ground, and the next root element 210 is lifted up via cable 260. This is exemplarily shown in FIG. 10. For turning the rotor hub 320, an extra motor may be applied, for instance in the high speed section of the gear train in the nacelle. This motor may be removed after the mounting process is completed.

FIG. 11 shows a modular rotor blade 200 according to embodiments. The principle is similar to the rotor blade shown in FIGS. 3 and 4, with an additional pulley 380 mounted, preferably rotatably, in the tip element 230. Cable 385 enters root element 210 at opening 265 and protrudes through the segments 210, 220, 230, and is then being redirected by pulley 380. It then protrudes back through the elements 210, 220, 230, and the end portion 385 of the cable leaves root element 210 through opening 265. Thereby, the cable does not need to be attached to tip element 230 by clamping or the like. Further, as the pulley acts as a transmission, the force needed to attach the elements by pulling one end of the cable is significantly reduced, theoretically (when omitting friction) to half. Both portions of the cable may protrude through the same tubes 280, or through dedicated parallel tubes.

In embodiments where cables 260 include fiberglass, the strain in the cable during the tensioning process may be measured via optical sensors measuring the optical properties of the fiberglass cable. These sensors may also be used during operation of the wind turbine to control the state of the cables.

The above-described systems and methods facilitate installation of wind turbines in regions which are difficult to access, and which provide limited space during assembly.

Exemplary embodiments of systems and methods for wind turbines with modular rotor blades are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, modular rotor blades are not limited to implementation with only the wind turbine systems as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other rotor blade applications.

Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, those skilled in the art will recognize that the spirit and scope of the claims allows for equally effective modifications. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

1. A rotor blade for a wind turbine, comprising: a) at least two segments; and, b) at least one cable; wherein the at least two segments are adapted to be mounted together to form the rotor blade, and wherein the at least one cable is adapted to attach the at least two segments, and wherein the at least one cable is extending through at least part of the segments.
 2. The rotor blade of claim 1, wherein the at least one cable protrudes along a longitudinal axis of the rotor blade.
 3. The rotor blade of claim 1, wherein the rotor blade further comprises a tip portion and a root portion, and wherein the cable protrudes from the tip portion in a direction towards the root portion.
 4. The rotor blade of claim 1, wherein the cable is fixed at least one end portion of at least one segment.
 5. The rotor blade of claim 1, wherein the cable is fixed to at least one of the at least two segments via clamping or lamination.
 6. The rotor blade of claim 1, wherein the cable comprises one or more elements from the list consisting of: steel, stainless steel, fiberglass, and carbon fiber.
 7. The rotor blade of claim 1, wherein at least one of the segments further comprises at least one tube, and wherein the cable protrudes through at least a part of its length through the at least one tube.
 8. The rotor blade of claim 1, further comprising a sensor for tension measurement, adapted for detecting a strain in the cable.
 9. A wind turbine, comprising: a) a tower; b) a nacelle; c) at least one rotor blade, including: i) at least two segments; and, ii) at least one cable; wherein the at least two segments are adapted to be mounted together to form the rotor blade, and wherein the at least one cable is adapted to attach the at least two segments, and wherein the at least one cable is extending through at least part of the segments.
 10. The wind turbine of claim 9, further comprising a winch adapted for tensioning the at least one cable.
 11. The wind turbine of claim 10, wherein the winch is located in one of the hub or the nacelle.
 12. The wind turbine of claim 9, further comprising an auxiliary motor for turning the hub.
 13. The wind turbine of claim 12, wherein the auxiliary motor is located in a high speed section of a gear train in the wind turbine nacelle.
 14. A method for assembling a rotor blade for a wind turbine, comprising: a) providing at least two segments; b) providing at least one cable; c) fixing at least one first end of the at least one cable to at least one segment; d) tensioning an at least one second end of the cable in order to attach the at least two segments to each other; and, e) fixating the at least one second end of the at least one cable.
 15. The method of claim 14, wherein fixating the at least one second end comprises clamping.
 16. The method of claim 14, wherein tensioning an at least one second end of the cable is carried out by a winch.
 17. The method of claim 14, further comprising: a) mounting a hub of a wind turbine to the nacelle at the wind turbine tower; b) lifting a first segment of a first rotor blade to the hub; c) fixating the segment to the hub; d) lifting a further segment; e) attaching the further segment to the previous segment; f) repeating d) and e) until all segments of a rotor blade are lifted to their positions; and,
 18. The method of claim 17, further comprising: g) turning the hub and the mounted rotor blade; and, h) repeating a) to f).
 19. The method of claim 17, wherein lifting a segment is carried out by a winch.
 20. The method of claim 19, wherein the winch is mounted to the hub. 